These perfluorinated aldehydes are useful as starting materials for the synthesis of chemical products containing a perfluorinated chain and which can be used, for example, as a surface agent. In particular, they can be reduced to polyfluorinated alcohols R.sub.F --CH.sub.2 OH.
Among the various currently known access routes to these perfluorinated aldehydes the following may be mentioned more particularly:
(1) The ozonolysis of compounds of the type CF.sub.3 (CF.sub.2).sub.n CH.dbd.CHR, which makes it possible to obtain aldehydes of the type CF.sub.3 (CF.sub.2).sub.n CHO directly in a 25% yield. See German Patent No. 2,556,844 and British Patent No. 1,473,807.
(2) The reaction of perfluorobutyronitrile with a magnesium compound such as isopropylmagnesium bromide, leading to the formation of 37% of perfluorobutyraldehyde. See McBee et al., J. Am. Chem. Soc., 77, 917 (1955).
(3) The reaction of tetrafluoroethylene with (CF.sub.3).sub.3 C--CH(NMe.sub.2).sub.2 leading, after hydrolysis, to the aldehyde (CF.sub.3).sub.3 C--CF.sub.2 --CF.sub.2 --CHO. See Zeifman et al., Dokl. Akad. Nauk., SSSR, 265, 2, 347 (1982).
It is also possible to report the preparation of acetylenic perfluorinated aldehydes R.sub.F C.tbd.C--CHO in a yield of between 15 and 40% by a Wittig reaction between a perfluorinated acid chloride R.sub.F COCl and a phosphorus ylide of the type (C.sub.6 H.sub.5).sub.3 P.dbd.CH--CHO, followed by a pyrolysis at 220.degree. C. and 1333 Pa (Shen Yanchang et al., Synthesis, 2, 159 (1985)), as well as the preparation of perfluorobenzaldehyde in a yield of 40% by reaction of perfluoro-phenyl-lithium with N-methylformamide (Coe et al., J. Chem. Soc., 3227 (1962)) or in a yield of 62.4% by reaction of perfluorophenylmagnesium chloride with N-methylformanilide (Vorozhtsov et al., Dokl. Akad. Naut., SSSR, 159, 125 (1964) and CA, 62, 4045a (1965)).
It is further known, that perfluoroalkyl iodides R.sub.F I react with the zinc-copper metal couple and substrates such as SO.sub.2 or CO.sub.2, in dimethyl sulphoxide or dimethylformamide, to lead to zinc sulphonates and carboxylates, precursors of the corresponding perfluorinated acids. See French Patent Nos. 2,342,950; 2,373,503 and 2,374,287. It is also known that polyfluorinated iodides of the type R.sub.F CH.sub.2 CH.sub.2 I react with zinc-copper couple in dimethyl sulphoxide or dimethylformamide to produce the fluorinated alcohols R.sub.F CH.sub.2 CH.sub.2 OH after oxidation with gaseous oxygen and hydrolysis. See French Patent No. 2,521,987. These known reactions have been carried out in the absence of a radical initiator.
The above references are hereby incorporated by reference herein.